机柜地线接至贯通地线，接地电阻≤（）。
A.0.5Ω
B.1Ω
C.2Ω
D.4Ω
参考答案：B
---Excuse me, could you please tell me if the match will be held on time?
---It depends on the weather. If it rains tomorrow, we’ll have to ______ it ______.
A．turn … on
B．put …off
C．take … away
D．look …up
额定电压相同，额定功率不同的两个灯泡能否串联使用？
